This invention pertains to resonant systems and more particularly to stepping motor systems which are optimally driven by exploiting the resonant properties between the stator field and the rotor.
In the copending U.S. Applications Ser. No. 876,656 filed Jan. 6, 1978, now U.S. Pat. No. 4,215,302 and Ser. No. 082,742 filed Oct. 9, 1979, now U.S. Pat. No. 4,280,084 there is disclosed new apparatus and methods for driving conventional stepping motors. In particular the apparatus and methods relied upon among other things, particular current waveforms with certain amplitudes for energizing the windings of the stator. These amplitudes were derived by exploiting the resonant properties of the system. The disclosure of such apparatus and methods has created a demand for even more versatile devices. In particular, it has been discovered that the load connected to the stepping motors can be changed for certain applications. For example, if the stepping motor is being used in a printer utilizing interchangeable "daisy" wheels for different type fonts, the problem arises in that each wheel may have a different mass. Accordingly, the load on the rotor will change. The changing of this load in effect changes the resonant properties of the system. Accordingly, the original driving current amplitudes will no longer be optimum.
In other instances it is necessary to know the torque of the motor because from the torque parameter and the moment of inertia parameter one can also determine the required driving currents.